BIOD 171 Module 5 Exam – Essential
Microbiology 2027 Update
Portage Learning / Geneva College
1. Define the concept of universal precautions.
*Universal precautions means any and all samples, whether known or unknown,
are to be treated as potentially hazardous (or pathogenic) materials. *
Rationale: Universal precautions require that all biological samples be handled with equal
caution because the infectious status may be unknown. This protective principle ensures
worker and public safety by assuming the presence of infectious agents in any specimen .
2. List at least 3 observations a researcher would be sure to note while assessing an
unknown microbial sample.
*1. Size and shape 2. Any observable motility 3. Gram status (positive or negative)
4. The presence of any chemical reactions 5. Changes in color localized to the
organism or the surrounding media 6. Capture (or draw) images of any of the
characteristics described above *
Rationale: Systematic observation of morphological characteristics, motility, and staining
properties is essential for preliminary identification of unknown microorganisms .
3. While observing an unknown sample of limited amounts, a researcher must
determine motility and Gram status using the same sample—the liquid cannot be
divided. Which would you determine first and why?
*You must determine motility before determining the Gram status. Motility
requires a wet mount, while Gram staining requires heat fixing the sample. If one
were to begin with the Gram stain, the heat fixation process would kill the
organism, making any observations regarding motility impossible. The correct
approach would be to place the liquid culture on a glass slide and determine its
,motility status. Next, the same liquid culture can be heat fixed and Gram
stained. *
Rationale: The correct approach is wet mount first for motility observation, then heat
fixation for Gram staining .
4. A facultative anaerobe is a microorganism capable of growth under what
conditions?
*A facultative anaerobe is capable of growth under aerobic (with oxygen) and
anaerobic (without oxygen) conditions. *
Rationale: Facultative anaerobes can metabolize energy aerobically when oxygen is
present but can switch to fermentation or anaerobic respiration when oxygen is absent .
5. As Streptococcus is catalase negative, would it thrive or die in the presence of
peroxides? Why?
*Streptococcus would not survive in the presence of peroxides—it is unable to
breakdown peroxides (catalase negative). Left unchecked, peroxides would
damage the cellular integrity of Strep causing lysis/cell death. *
Rationale: Catalase is the enzyme that breaks down hydrogen peroxide into water and
oxygen. Without it, peroxide accumulates and damages the cell .
6. Streptococcus is most often streaked onto:
A) Chocolate agar
B) Blood agar
C) EMB agar
D) Spirit Blue agar
*B) Blood agar *
,Rationale: Strep is often cultured on Blood agar plates to determine its hemolytic
properties (alpha, beta, or gamma hemolysis), which aids in classification and
differentiation .
7. True or False: The Lancefield groups are used to subdivide antigenic groups of
gamma-hemolytic Streptococcus.
*False *
Rationale: The Lancefield groupings are used to subdivide beta-hemolytic Streptococcus,
not gamma-hemolytic Strep .
8. The distinctions for Lancefield subgroupings lie in its:
A) Hemolytic activity
B) Catalase activity
C) Carbohydrate composition of antigens
D) All of the above
*C) Carbohydrate composition of antigens *
Rationale: Carbohydrate composition of antigens present in the cell wall determines the
Lancefield groupings (A, B, C, etc.). All Strep under Lancefield groupings are catalase
negative and beta-hemolytic .
9. Left untreated, strep throat can progress to ______, which displays _____ hemolytic
activity.
A) Strep. Pharyngitis; alpha
B) Rheumatic fever; beta
C) Strep. Septicemia; gamma
D) Strep. Pharyngitis; beta
, *B) Rheumatic fever; beta *
Rationale: Strep throat (also known as strep pharyngitis) can lead to Rheumatic fever if left
untreated. Strep pharyngitis displays beta-hemolytic activity .
10. True or False: Under most circumstances, Staphylococcus can be found in
~30% of the human population where it remains pathogenic.
*False *
Rationale: While Staphylococcus can be found in ~30% of the human population, it
remains non-symptomatic (commensal), not pathogenic .
11. Define commensal bacteria.
*The bacterium neither harms nor benefits from the host from which it obtains
nutrients. *
Rationale: Commensal bacteria derive nutrients from the host without causing harm or
providing benefit. This represents a neutral symbiotic relationship .
12. How can Staphylococcus be differentially tested?
*Staphylococcus species are capable of growth in the presence of bile salts (MSA
agar). *
Rationale: Mannitol Salt Agar (MSA) contains bile salts and high salt concentration, which
inhibit most bacteria but allow Staphylococcus to grow, allowing differential identification
.
Microbiology 2027 Update
Portage Learning / Geneva College
1. Define the concept of universal precautions.
*Universal precautions means any and all samples, whether known or unknown,
are to be treated as potentially hazardous (or pathogenic) materials. *
Rationale: Universal precautions require that all biological samples be handled with equal
caution because the infectious status may be unknown. This protective principle ensures
worker and public safety by assuming the presence of infectious agents in any specimen .
2. List at least 3 observations a researcher would be sure to note while assessing an
unknown microbial sample.
*1. Size and shape 2. Any observable motility 3. Gram status (positive or negative)
4. The presence of any chemical reactions 5. Changes in color localized to the
organism or the surrounding media 6. Capture (or draw) images of any of the
characteristics described above *
Rationale: Systematic observation of morphological characteristics, motility, and staining
properties is essential for preliminary identification of unknown microorganisms .
3. While observing an unknown sample of limited amounts, a researcher must
determine motility and Gram status using the same sample—the liquid cannot be
divided. Which would you determine first and why?
*You must determine motility before determining the Gram status. Motility
requires a wet mount, while Gram staining requires heat fixing the sample. If one
were to begin with the Gram stain, the heat fixation process would kill the
organism, making any observations regarding motility impossible. The correct
approach would be to place the liquid culture on a glass slide and determine its
,motility status. Next, the same liquid culture can be heat fixed and Gram
stained. *
Rationale: The correct approach is wet mount first for motility observation, then heat
fixation for Gram staining .
4. A facultative anaerobe is a microorganism capable of growth under what
conditions?
*A facultative anaerobe is capable of growth under aerobic (with oxygen) and
anaerobic (without oxygen) conditions. *
Rationale: Facultative anaerobes can metabolize energy aerobically when oxygen is
present but can switch to fermentation or anaerobic respiration when oxygen is absent .
5. As Streptococcus is catalase negative, would it thrive or die in the presence of
peroxides? Why?
*Streptococcus would not survive in the presence of peroxides—it is unable to
breakdown peroxides (catalase negative). Left unchecked, peroxides would
damage the cellular integrity of Strep causing lysis/cell death. *
Rationale: Catalase is the enzyme that breaks down hydrogen peroxide into water and
oxygen. Without it, peroxide accumulates and damages the cell .
6. Streptococcus is most often streaked onto:
A) Chocolate agar
B) Blood agar
C) EMB agar
D) Spirit Blue agar
*B) Blood agar *
,Rationale: Strep is often cultured on Blood agar plates to determine its hemolytic
properties (alpha, beta, or gamma hemolysis), which aids in classification and
differentiation .
7. True or False: The Lancefield groups are used to subdivide antigenic groups of
gamma-hemolytic Streptococcus.
*False *
Rationale: The Lancefield groupings are used to subdivide beta-hemolytic Streptococcus,
not gamma-hemolytic Strep .
8. The distinctions for Lancefield subgroupings lie in its:
A) Hemolytic activity
B) Catalase activity
C) Carbohydrate composition of antigens
D) All of the above
*C) Carbohydrate composition of antigens *
Rationale: Carbohydrate composition of antigens present in the cell wall determines the
Lancefield groupings (A, B, C, etc.). All Strep under Lancefield groupings are catalase
negative and beta-hemolytic .
9. Left untreated, strep throat can progress to ______, which displays _____ hemolytic
activity.
A) Strep. Pharyngitis; alpha
B) Rheumatic fever; beta
C) Strep. Septicemia; gamma
D) Strep. Pharyngitis; beta
, *B) Rheumatic fever; beta *
Rationale: Strep throat (also known as strep pharyngitis) can lead to Rheumatic fever if left
untreated. Strep pharyngitis displays beta-hemolytic activity .
10. True or False: Under most circumstances, Staphylococcus can be found in
~30% of the human population where it remains pathogenic.
*False *
Rationale: While Staphylococcus can be found in ~30% of the human population, it
remains non-symptomatic (commensal), not pathogenic .
11. Define commensal bacteria.
*The bacterium neither harms nor benefits from the host from which it obtains
nutrients. *
Rationale: Commensal bacteria derive nutrients from the host without causing harm or
providing benefit. This represents a neutral symbiotic relationship .
12. How can Staphylococcus be differentially tested?
*Staphylococcus species are capable of growth in the presence of bile salts (MSA
agar). *
Rationale: Mannitol Salt Agar (MSA) contains bile salts and high salt concentration, which
inhibit most bacteria but allow Staphylococcus to grow, allowing differential identification
.
